# What is the NCX table of contents?

Source: https://epubcc.com/glossary/ncx/ (updated 2026-11-04)

The NCX (Navigation Control file for XML) is the table of contents format of EPUB 2, an XML file with the media type application/x-dtbncx+xml. EPUB 3 replaced it with the HTML navigation document but still allows an NCX for older readers.

## Why it matters when you convert a PDF to EPUB

An EPUB 3 made from a PDF needs a navigation document; adding an NCX as well only helps very old reading systems. If an NCX is present, its identifier must match the package's unique identifier, which is a frequent EPUBCheck error after editing metadata by hand.

How EpubCC handles it: it does not write an NCX. Its EPUB 3 output carries only the HTML navigation document, which is what current reading apps read; a very old device that only understands EPUB 2 may show no table of contents. Leaving the NCX out also avoids the identifier mismatches that EPUBCheck reports when the NCX and the package disagree.